Telephone switching systems are commonly used to control communication in a telephone switching network. These systems hereto comprise functional units called "switching centers" which provide functions mainly for setting up and terminating telephone connections between end devices of participiants of the switching network. Further, among others, functions are provided for forwarding telephone calls from a called person to a third person and for setting up telephone conference connections among multiple subscribers.
Thereupon these systems manage participant admission rights and rules control the adjustment of telephone end-devices, and record information about telephone connections having been switched, e.g. for telephone book-keeping or accounting purposes.
In order to provide the above functionality of circuit switched telephone networks in computers, recently Computer-Telephone Integration (CTI) applications have been developed. Hereby the functionality of switching networks is combined with functions of classical information processing. Exemplary CTI systems are a class of applications called "Call Centers" which enable routing of telephone calls to suitable contributors or colleagues of a called participant, and which provide a computer user with utilities allowing activation of telephone functions out of a standard application environment. Another class of applications are dialing support tools in the arena of telebanking.
In a common architecture of existing CTI applications as depicted in FIG. 1, a first computer 1 is connected to a telephone switching system 2 over a physical interface 3, for instance, the interface definition standard "V24" or the standardized Integrated Services Digital Network (ISDN). Through that connection, control commands and messages can be exchanged between the first computer and the switching system according to a defined communication protocol. On the other side, a second computer 4, as a server for the locally or distantly located applications (clients), provides the functionality of the switching system to the applications.
There exist a number of proprietary or standardized CTI interfaces like the "TSAPI" by Novell, "TAPI" by Microsoft/Intel, "CallPath" by IBM. In general, the switching network functions are provided to the application programs through an application program interface (API). Those approaches are broadly discussed in an overview article by T. Nixon, entitled "The Design Considerations for Computer-Telephony Application Programming Interfaces and Related Components" and published in IEEE Communications Magazine vol. 34, no. 4 (1996), pages 43-47.
An approach where a server is attached directly to a telephone switch--in contrast to a concept where a LAN server has to pass telephony signalling to the telephone switch (PBX) over the LAN--is disclosed in an article by S. Rudd, entitled "Where do CTI Applications really belong?", published in Business Communications Review, vol. 26, no. 2 (1996), pages 23-26. the advantage of that concept is that a CTI application not tightly coupled with LAN-attached databases will perform far better and cost much less.
A comparison between known mainframe PBX systems and an approach where a widely distributed group of CTI servers is linked through an isochronous broadband backbone, is given in an article by L. Goldberg, entitled "CTI Computer/Phone Fusion at LAN's Edge" and published in Electronic Design vol. 42, no. 22 (1994), pages 77-90. These servers can be configured to route calls, or they also may take on more specialized functions such as becoming an interface to a public switch telephone network (PSTN) by acting as an automated attendant, voice-mail server, or any other network service.
There exist further generic solutions in the field of voice mail systems which are directly attached to the Internet. A telephone call can be performed via a so-called Webphone service. Another example of a system is "DirectTalkMail" by IBM. Another voice mail system is disclosed in PCT application WO . . . entitled "Voice Mail System" and assigned to the present assignee (Docketno. UK995024). That system provides access to voice mail over the Internet's World Wide Web. A user has to call up a page associated with a specific voice mail system and to enter a mailbox number. A WWW server responds by transmitting a message to the voice mail system itself. A further request may be directed from the server to the voice mail system, which results in the voice mail system returning the actual audio data for the message to be played to the user.
In an article by R. Sergeant disclosed in IBM Technical Disclosure Bulletin vol. 38, no. 8 (1995), pages 415-418, and entitled "Inexpensive Multimedia Facility for Workstation", an arrangement is described which allows a same graphical user interface (GUI) to be utilized when a standard desk telephone is used as audio input/output device. The GUI application sends a comment to a CTI server to ring the telephone at the user's desktop and to set up a connection.
A desktop telephone approach can also be integration of Lotus Notes by Lotus Development Corporation (IBM), where client specific modules handle messages received by a CTI server. These modules communicate via local Inter Process Communication (IPC) means with a Lotus Notes client. The Notes client then starts the appropriate actions for the Notes application, depending on the messages received, e.g. "Open specific Databasees/Database entries" or "Start application specific actions".
Further in IBM Technical Disclosure Bulletin vol. 37, no. 1 (1994) pages 357-358, a "Global Multimedia Hyperspace" concept is disclosed. According to that concept, in case no direct network link exists between two hyperdocument nodes, a telephone link is established between two corresponding computer systems. The hyperlinks need not be simply a local address, instead, it can be a telephone link to a node residing inside another hyperlinked document anyplace in the world. The advantage of this approach is integration of the world in a way analogous to the global Internet, global TV network or the global telephone network.
Known CTI solutions are integrated on a server, like Novell's Telephony Server, and thus have the drawback that due to the various different operating system platforms, in particular in the area of Personal Computers or Workstations, an interface has to be adapted to each client's platform i.e. to be compatible with multiple different operating systems.